1. Technical Field
The present invention generally relates to a high-order harmonic wave generation apparatus and, more particularly, to a high-order harmonic wave generation apparatus that uses a diode-pumped solid state laser device, with which a wavelength may be selected.
2. Description of the Related Art
Generally, ultraviolet laser light is generated through frequency conversion of infrared light using a nonlinear optical crystal.
To this end, a nonlinear optical crystal may be selected from among beta barium borate (beta-BaB2O4, BBO), lithium tri-borate (LiB3O5, LBO), potassium titanyl phosphate (KTiOPO4, KTP), cesium lithium borate (CLBO), and lithium niobate (LiNbO3) in consideration of the phase-matching conditions of the nonlinear crystal, the polarization of incident light, and the like. Also, the effective conversion of wavelength may realize light pulses having high peak power, such as a Q-switched laser, and such high-output energy may be obtained mainly through a side-pumping scheme.
In particular, because the short wavelengths of an ultraviolet laser beam may highly enhance the intensity of signals from Raman scattering and avoid background noise, they have come into the spotlight and are widely used in the fields of primary research, basic industry, and the munitions industry.
However, a high-output energy laser system requires that a large amount of heat, resulting from energy that has not been converted into laser light, be removed using coolant, thus being inconvenient to manage and increasing the size of the system.
Also, a Fabry-Pérot laser resonator, commonly used in industrial applications, is very sensitive to optical axis alignment, external vibrations, and temperature. Therefore, when an ultraviolet laser beam is used outdoors, the Fabry-Pérot laser resonator is unsuitable because it requires environmental resistance.